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I N - K -QUAL - 6 7 - 8 3
E V A L U A T I O N O F P O S T S O L D E R I N G
C L E A N I N G A G E N T S
F. C. Osemlak
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RELLABILITY :ASSURANCE Q U A L I T Y AND LA BORA TORY GEORGE C. MARSHALL SPACE FLIGHT CEILTER
Huntsville, Alabama % I
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F O R I N T E R N A : L U S E O N L Y
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https://ntrs.nasa.gov/search.jsp?R=19700028216 2020-06-28T15:00:38+00:00Z
May 22, 1967
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IN - R - QUA L - 6 7 - 8
EVALUATION OF POSTSOLDERING
CLEANING A ~ E N T S ,
1 F
BY F. C : Osemlak
A BSTRA C:T
5 This r epor t p re sen t s the testing r e su l t s of a selected number of
1 postsoldering cleaning agents with respec t to cleaning effectiveness, compatibility with different ma te r i a l s u'sed in pr inted c i rcu i t a s sembl i e s , and duration of individual solvent cleaning cycles that could be tolerated without adve r se effects and chemical cha rac t e r i s t i c s . /
The r e su l t s indicate that the de t r imenta l effects of solvents / 1 I I i
differ with the composition of the matel ' ials used in pr inted c i rcu i t board assembl ies . The choice of cleaning agents mus t be specifically for the intended application, and it is necessar:y to pe r fo rm t e s t s on individual assembl ies representa t ive of the work to be processed .
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E LE C T R I C A L ANA LYSIS SE C TION E L E C T R I C A L TEST A N D A N A L Y S I S B R A N C H
A N A L Y T I C A L O P E R A T I O N S DIVISION
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May 22, 1967 IN - R - QUA L - 6 7 - 8
EVALUATION O F POSTSOLDERING
CLEANING AGENTS I
BY
F. C. Osemlak'k
3
SUMMARY
P r e l i m i n a r y investigation in the evaluation of cleaning agents for the r emova l of flux res idues and contaminants which may be p r e s e n t on pr inted c i r cu i t boards , components o r a s s e m b l i e s a f t e r the so lder ing operat ion has indicated that this study could be mos t effectively pursued in two p a r t s .
The f i r s t s e r i e s of t e s t s were se lec ted to provide data on cleaning effect iveness of solvents . The second group of evaluations was chosen to furn ish information regarding compatibil i ty of solvents with different ma te r i a l s used in pr inted c i r cu i t a s sembl i e s and durat ion of individual solvent cleaning cycles that could be to le ra ted without degrading effects on the m a t e r i a l s .
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Considerat ion of these fac tors has shown that a "universal type solvent" is not avai lable . Det r imenta l effects of solvents differ with the composition of the m a t e r i a l s used 'in the pr inted c i r cu i t a s sembl i e s and the methods which a r e employed in accomplishing the removal of' flux res idues and Contaminants. The select ion of the cleaning agent is dependent upon the intended application,and i t is concluded that it is e s sen t i a l that p re l imina ry t e s t s on a s s e m b l i e s representa t ive of the work to be p rocessed be pe r fo rmed .
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all Space F l ight Center , under ;Contract No. NAS8 -20081.
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IN - R -QUA L- 6 7 -8
TABLE O F CONTENTS
Sect ion P a g e
, I INTRODUCTION 2
A . General . . . . . . . . . . . . . . . . . . . . . . . . . . 2 I B. Solvent Charac t e r i s t i c s . . . . . . . . . . . . . . . 3
. . . . . . . . . . . . . . . . . . . . . . . .
I
OBJECTIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 , I
T E S T P R O G R A M . . . . . . . . . . . . . . . . . . . . . . . . 5
IV
A . Solvent Cleaning Effect iveness . . . . . . . . . . . B. Component and Mater ia l s Compatibility
With Solvent . . . . . . . . . . . . . . . . . . . . . . CONCLUSIONS . . . . . i . . . . . . . . . . . . . . . . . . .
. I ! s I
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IN-R-QUAL-67-8
MFG.
Du Pont
Du P o n t
Du Pont
TRADE NAMES AND SYMBOLS
TRADE N A M E O R CHEM NOMENCLATURE
Methylene Chloride
T r ic hloroethane
T r i c hlo rot r i f luoroe thai
F r e o n T F
F r e o n TA
F r e o n TE-35
Du Pont F r e o n TC
Allied Genesolv DTA Chem i c a1
Du Pont F r e o n TMC
Alpha 563
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i v,
;A L COMPOSITION
CH2Cl 2 HZCCIZ
CH2Cl CHC1
C C12F C C1 F2
T r ic hlo ro t r i flu0 roe thane
Azeotrope of F r e o n T F and Acetone
Blend of F r e o n T F a n d . . Ethyl Alcohol
Azeotrope of Fr.eon T F and Chloroform
A z eot rope contain ing Tr i c h - lo ro t r ifluo roethane, meth yiene chlor ide and methyl alcohcjl
Azeotrope containing E'reon T F and Methylene Chloride
Chloronated ;i-f :rdroca r Lon (p r op r ie ta r y)
3
IN-R-QUAL-67 -8
SECTION 1. I N ~ R O D U C T I O N
A . ' GENERAL 1
I It h a s been found that the capability of a solvent to remove
rcs idues and contaminants a f t e r the so lder ing operat ion without injurious effects upon the ma te r i a l s of a .pr in ted c i r cu i t a s sembly depends upon a number of va r i ab le s , among these a r e :
1. Soldering Flux Used. The kind and amount of flux I I
'
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r es idue remaining is dependent to a l a rge extent upon the chemica l com- posit ion of the flux used. ta in , in addition to the base solvent, ' m a t e r i a l s which a c c e l e r a t e thc- removal of the metal oxides and contaminants which could in te r fe re with the making of the requi red so lde r - to ibase me ta l bond. removal is des i r ab le , s o m e of the flux res idues which remain have been found to be co r ros ive to the e l ec t r i ca l a s sembl i e s making it mandatory tha t the flux ma te r i a l s remaining a f t e r the solder ing be removed.
I The "activated" type of flux w i l l usually con-
Whereas this
2. T ime Elapsed Between Soldering Operation and Flux The solidification and p rogres s ive hardening of flux Residue Removal.
res idue m a t e r i a l s and o the r entrapped contaminants which may be p r e s e n t upon drying r equ i r e s additional cleaning t ime and specif ic techniques for removal . shr inkage which reduces the porosi ty making it m o r e difficult for t h e cleaning solvent to pene t ra te and bring the ma te r i a l s into solution f o r r e m oval.
The r eason for this being:that as the m a t e r i a l s d r y t h e r e is ;i
3. Size, Shape, and Number of Componcnts to be Clcaned. Components containing a r e a s with dep res s ions , p roximate to o ther c'om - ponents o r to the mounting base make it m o r e difficult to achieve t h e requi red circulat ion of the cleaning agent for complete removal of the res idues and contaminants . s i t y to del ineate techniques of cleaning in conjunction with the choice of cleaning agent .
These a r e f ac to r s that emphas ize the neces -
4. Component, Base Board, and Marking Mate r i a l s . Manufac turers of e lec t ronic a s sembl i e s in p rac t i ce obtain subassembi ies and individual components f rom a number of suppl ie rs who in turn employ multiple s o u r c e s of supply. pletely removed on s o m e componentjs and show li t t le o r no effect on othc.;
' In labora tory testing, markings a r e 1 , J ~ : -
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IN - R - QUA L - 6 7 - 8
components after cleaning with the s a m e solvent. extended to include base board and component ma te r i a l s .
This effect may he
5 . Nature of Fore ign Contaminants to be Removed. A s w i l l be d iscussed l a t e r , ma te r i a l s of different origin, organic o r in- organic , may be dissolved by different types of solvents. The d e t e r - mination of the kinds of contaminants, o ther than flux res idues , can be aided by a knowledge of the his tory of the assembly . The knowledge of s torage d i r t accumulation, persp i ra t ion oi ls due to manual handling, and lubricating compounds f rom mate r i a l t r a n s f e r equipment can a s s i s t in the choice of the cleaning agent.
6. Corros iveness of Solvent Residue. A s the degrev of Contamination p r o g r e s s e s , a m o r e vigorous type of cleaning agent is required, The limiting factor in cleaning agents employed for e lcc - t ronic assembl ies is the immediate effects on the ma te r i a l s being sub- jected to cleaning and the possibil i ty of a t tack of the ma te r i a l s by the solvent res idue a f t e r the assembly i s put to end-item usage.
F r o m these considerations it can be seen that a "universal type solvent" is not readily determined, but that the c leaner to be used and the number of cleaning, cycles and the i r duration will be dependent upon the individual assembl ies . specific to the application involved.
It is necessa ry to conduct t e s t s which a r e
B. SOLVENT CHARACTERISTIGS
Solvents may be broadly cla@eif ied as being polar o r nonpolar with intermediate degrees of eirniliatrity to tka~~ci . t w o elis;s,si- f ications; therefore , i t should be r emembered that thesee teyms are re lat ive r a t h e r than absolute. In general , it may be said thibt pofiaar solvents w i l l d issolve polar ma te r i a l s such as ac idsb bases , salts, and mate r i a l s ionic in na ture and are associated wi th high dielectr ic con- s t an t s . Chemically, polar solvents contain the hydroxy o r k r t o n i r a groups i . e . , alcohols, acetone, The nonpolar oolvcnts have a l o w dielectr ic constant as typified by the hydrocarbon benzene and are m o r e likely to dissolve nonpolar subBtance8 such a d fate and o i l @ ,
Among the physical propertie6 that are deuirablr in a, csolv~rtt a r e :
(1) Low viscosi ty - A l l o w s fas t drainage o f +rts following removal f rom solvent.
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IN- R - QUA L-67-8
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Low sur face tension - P e r m i t s penetrat ion into p o r e s , . c r a c k s , and s m a l l openings.
High density - A l l o w s res idues to be held in s us pens ion ., ,
Stability - Unreactive with o the r chemica ls , par t icu lar ly with oils and o ther hydrocarbons. Resis tance 'to decompositiou upon exposure to light and a i r .
I
Considerations of economics toxicity, method of recovery of solvent, e t c . , are proper ly in the area of the cha rac t e r i s t i c s of indivi- dual manufactur ing p r o c e s s e s to which these fac tors a r e left for evaiu- ation.
I I
SECTION 11. ~ B J E C T I V E / .
The evaluation procedure in {his investigation w a s designed to furnish da ta bear ing upon the followfng solvent c leaner cha rac t e r i s t i c s :
Cleaning eifect iveness .
CompatibilFty with ma te r i a l s used in pr inted c i rcu i t ass 'emblies.
Duration of individual solvent cleaning cyc les that could be tolerated without adve r se effects .
Chemical dharac te r i s t ic s !
To dete a loop c
of a l iq i melted t h e n cie fol l0wr.c a micro r e p e at ($1
QQ-S - 5
F l u x
Alpha.
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IN - R -QUA L - 6 7 - 8
SECTION 111. TEST PROGRAM
I
A . SOLVENT CLEANING E@FECTIVENESS
1 . Solvent Cleaning. Effectiveness of Solder Flux Residues. -
T o de te rmine the cleaning effectiveness of the solvents on flux res idues , a loop of solid wire so lder conforming to type SN 60 W S of Specification QQ-S-571 was placed on a bright copper coupon (2" x 2") and five drops of a liquid solder ing flux were added to the so lder loop. The so lder was mel ted at 205O C, the t e s t coupon allowed to cool and'the sur face w a s then cleaned by immers ing the coupon in the cleaning solvent for 30 seconds followed by rubbing with Cel -F ibe wipes. a microscope using a maximum of 20X magnification. repeated for each solvent on all of the <tested so lder fluxes.
Inspection was per formed with This procedure was
Flux Sample Alpha 100 Alpha 61 I Alpha 7 1 1 ' '
Dunton Rosin X Dutch Bo) 110 F a r r e 110 y #8 Kes te r 1544 Kes ter 1 3 5
Resul ts : Cleaning Effectiveness I Solvents I
?reor I'MC
A
A
B
A
B
Bt
B
B
Freo TE B
B
Bt
B
B
B
B
B
~
Series o l v DTA Bt
B
.B t
B
B
Bt
A
Bt
- 41phi 563
B
B
B+
B
B
Bt
B
B
-
- sating Designations :
A Complete Removal Bt - Removal l e s s than B - Incomplete remova C - No removal .
5
Freer
C
B
C
C
C
C
C
B
TF Trichlo- roe t hane Bt
A
Bt
A
A
B
B
B
Methylene Chloride
A
A
A
A
A
A
A
__-.-- --I
Ethyi i j i
I3 I i
B
A i I i
B
n
Alcohol 4 B 3
I
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I
B I
B ; I 3 I
i f Remaining Flux. 00010; m o r e than 90%.
IN-R- QUAL-67-8
Cleaning Effectiveness
- A - Complete Cleaning
B t -More than 90% l e s s than 100%
R- Incomplete Cleaning
C-No removal of res idues
D-Surface film deposit
B.
F r e o r TMC
X 1
2. Solvent Cleanine Effectiveness of P C Boards A f t e r Dip-Spin Coating. dip-spin process : on an Elec t rover t machine using Kes te r 1544 Flux, K e s t e r 6 3 / 3 7 ASTM Clas s A so lder and peanut oils a t a t empera tu re of 465" F. The boards w e r e then subjected to a 30-second the solvents being tes ted and wip.ed with Gel-Fibe wipes.
Cleaning of pr inted c i r cu i t s solder coated by the Eight pr inted cirlcuit boards were dip-spin solder coated
immers ion w i t h mi ld agitation in
of solvent m e r s i o n i
Freon I'E
X
Solven
Senesol \ DTA
X
6
? reor T F
-
X
1, 1 , 1 I? r i c hlo - roethane
X
Me thy - Len e Chloride
X
! x l x i I 1
i I
Solvent
IN - R - QUA L-67-8
B. COMPONENT AND MATERIALS COMPATIBILITY WITH SOLVENT
1. Effects of Cleaning Agents on Formica . The effects of solvents on printed c i r cu i t board materials was determined by im- mers ion in the cleaning solvents f o r varying controlled per iods of t ime.
Fo rmica , Grade - F F - 9 1 NEMA - G - 10 MIL-P-18177 - C GEE
Solvent
Genesolv DTA
Alpha 563
F reon TE
Freon TMC
T F (not mixed)
Ethyl Alcohol
1, 1, 1 , Trichloc roe thane
Me th y 1 en e Chlo r ide
30 See, - 1
1
1
1
1
1
1
1
Immers ion Time
1 Mine
1
1
1
1
1
1
1
1
3 Mini
2
1
1
2
1
1
1
2
5 Min
2
1
1
2
1
1
1
2
--
l o Min _II
2
1
2
2
1
1
1
2
-- 30
Mine
2
1
2
2
1
1
1
--
2
w Loss of adhesion between %aminatiano
1. No visible effect.
2. Slight bubbling and softening,
3. E x t r e m e softening,
4, Dis int e g ration e
7
IN-R-QUAL-67-8
3 . E 3 Coating.
Solvent
F reon T F
F r e o n TMC
1, 1 , 1 , Trichlo roe thane
Alpha 563
Methylene Chloride
EPOXY - Hysol PC-12-007
Immers ion Time -.--
30 ;ec .
1
1
I
-
1
1
-
1 Min.
1
1
1
__I
1
2
-
3 Min.
1
1
1
-
1
2
5 Min.
1
2
1
1
3
10 Min.
1
2
2
1
3
3 0 Min.
1
2
2
1
4
s__
1 Hr.
1
3
2
__.
3.
4
-
c_
2 H r . 1
3
2
_I_
1
4
CI
NOTES: Epoxy coating was applied to pr inted c i r c u i t board (mica board) . N o effect w a s noted on base board.
Key to Table E n t r i e s :
1. N o v is ib le e f f e c t .
2. Slight bubbling and softening,
3 . Ext reme softening and blistering,
4. Complete disintegration of c n
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IN - R - QUAL- 67 - 8
4. Effects of Cleaning Agents on Silicone Conformal Coating.
Silicone Slygard # 18 2
Solvent
F reon T F
Freon TMC
1 , 1, 1 , Trichlo- roe t h ane
Alpha 563
Methylene Chloride
30 S e c .
Imm e r s ion Time
1 Min.
3
4
4
4
4
__I
3 Min.
5 Min.
10 Min .
30 Min.
4
4
4
4
4
I__
1 H r .
- 2
Hr .
- 4
H r .
NOTES: Silicone coatings were applied to pr in ted circui t . boards m a t e r i a l (mica board) .
Key to Table E n t r i e s :
1 . N o visible effect .
2 . Slight bubbling and softening.
3. Ex t r eme softening and blistering.
4. Complete dis integrat ion of coating.
10
IN - R - QUA L- 6 7 - 8
30 Sec.
5. Effec ts of Cleaning Agents on Acryl ic .
1 Min. Solvent
F reon T F
F r e o n TMC
1, 1, 1, Trichlo- roe t han e
Alpha 563
Methylene Chloride
Acry l ics Hurniseal 1B12
Immers ion Time
Min. Min. 1
Hr .
3
4
3
-
a
4
NOTES: Acryl ics coating was applied to pr inted c i rcu i t board m a t e r i a l (mica board) .
N o effect w a s noted on the board itself,
Key to Table E n t r i e s :
1. Ne, visible effect.
2 . Slight bubblin
3. E x t r e m e soft
4. Complete di ration of coating,
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IN - R - QUA L- 67 - 8
7 . Effec t s of Cleaning Agents on Res is tor (Carbon) .
Res is tors - Stock No. 215-0006056, Allen Bradley
Solvent
F reon T F ,------ Freon TMC I
1 , 1 , 1 , Trichlo roe thane
Alpha 563
Methylene Chloride
30 Sec. - 1
1
2
1
2
Immersion Time
1 3 Min. Min.
1 1 1
2 2
5 Min.
1
3
3
-
1
3
10 Min .
1
3
3
-
1
3
30 Min.
1
3
3
_I_
1
3
_I
4 H r . -
NOTES: Res is tors were completely i m m e r s e d into the cleaning agent. instance except as noted.
Color coding w a s bl is tered o r removed in every
Key to Table E n t r i e s :
1. N o visible effect ,
2,
3 .
Slight softening of color coding o r m
Extreme softening of color csdia
5 Complete deotruction of ~o~~~~~~~ m ~ t e r i d .
13
IN - R - Q U A L - 6 7 -8
8 . Effects of Cleaning Agents on Res i s to r s (Film Type).
Res is tors - Stock No. 215-0001739 P a r t N o . R 1 42AD152J
.__.
30 Solvent Sec.
r1 Freon T F
Freon TMC 1
1, 1 , 1, Trichlo- 1 roethane
Alpha 563 1
Methylene 2 Chloride I
Immers ion Time - 1
Min a
1
1
1
1
3
Min. Min. 3 1 5
- 10
Min. - 4
4
4
2
3
__L_
- 2
H r
4
4
4
-
3
5
__I
4 H r .
4
4
4
3
5
NOTES: Res is tors w e r e completely i m m e r s e d into solvent.
Key to Table E n t r i e s :
1 , N o visible effect.
2.
3 .
4, Softening of component material,
5 .
Slight softening of color codin
Ex t reme softening of color codi
Complete destruct ion of component m a t e r i a l .
14
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IN - R- Q U A L - 6 7 - 8
9.
Solvent
F reon T F
Freon TMC
1, 1, 1 , Tr ichlo roe t ha ne
Alpha 563
Methylene Chloride
Effects of Cleaning Agents on Diodes (Glas s ) .
Diodes - Class
- 30 iec. - 1
3
3
a
3
111
Immersion Time
5 Min. T Min. Min.
---I--- I
- 1 Hr . -
- 2
H r . II_
NOTES: Test was not continued due to the rapid removal of color c sding .
Key to Table Entr ies :
1. No v ie ib le effect,
2, Slight softening of color codifig or markings,
4 , Softening of eornpmarit material,
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IN - R - QUA L - 6 7 - 8
1
2
10. Effects of Cleaning Agents on Diodes.
1
2
Diodes 1N470
Immers ion Time I
1, 1 , 1 , Trichlo- roc thane
Alpha 563
Methylene Chloride
S o 1 vent
1 1
2 2
2 2
Freon T F
Freon TMC
3 Min.
30 Min.
- 1 Hr .
- 2
H r . 4
H r .
NOTES: Condition of diodes employed no changes during en t i r e length of t es t . N o fu r the r t ime w a s spent on this diode.
K e y to Table E n t r i e s :
1 . No v i s i b l e effect.
2. Slight softening of co lo r coding o r markings .
3 . E x t r e m e softening of co lar coding o r mark ing&.
4. Softening of component material .
5. Complete destruct ion of component material .
16
11.
Solvent
Freon TF
Freon TMC
1 , 1,' 1 , Tr ichlo- roe t han e
Alpha 563
Methylene Chloride
Effects of Cleaning Agents on Nylon.
Nylon Boards
Immers ion Time - 30
3,C.
1
1
1
-
1
1
_I_
NOTES: Hardness
5 Min.
1
1
1
-
1
1
-
10 Min. - 1
1
1
1
1
- 30
Min. - 1
1
1
1
1
_I_
- 1
H r .
1
1
1
-
1
1
-
- 2 Hr.
1
1
1
-
1
1
a
4 H r .
1
1
1
-
I
1
-- rest ing. A l l boards were tes ted with Shore B
hardness t e s t e r . of 65 Shore D. methylene chloride. s l igh t softening f rom 6 5 Share t o 58 Shere E>. However , no v is ib le effect was noticed.
The control board checked on average A l l solvents showed no effect except
Methylene chloride showed a v e r y
Key to Table Ent r ies :
1. N o visible effect.
2 . Slight softening o r bubbling.
3 . Ext reme softening o r bli
4.
5. Complete disintegration,
Separation of material with ~ s f t m ~ i a g and ott.t*tehing,
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I N - R - Q U A L - 6 7 - 8
12. Effects o f Clcaning Agents on Teflon.
Teflon Boards
Immers ion Time
Freon T F
Freon TMC
1, 1 , 1 , T r roethane
Alpha 563
Methylene Chloride
1 Min.
1
1
1
1
1
-
3 Min.
1
1
1
1
1
5 Min.
1
1
1
1
1
10 Min.
1
1
1
1
1
2 Hr .
1
I
1
I_
1
1
4 H r . II_
1
1
1
1
1
NOTES: Hardness Testing. A l l boards w e r e tes ted with Shore B hardness t e s t e r . 7 3 Shore D. A l l solvents showed no effect.
Control board checked an average a€
K e y to Table E n t r i e s :
1. No vis ib le effect .
2 . Slight softening o r bubbl ing,
3. Ex t r eme softening o r b l i s te r ing ,
4 . Separation of material . with softenin anst E%tretcking,
5 . Complete disintegration.
18
IN - R -QUAL- 67 -8
13. Effects of Cleaning Agents on Semiconductor Cans.
Semiconductor 5960 - LNI - 7940P GE - P/N-USAF-lN647
Freon TMC
N 0 'TES :
Key t o Table Ent r ies :
N o effect could be found.
1. N o visible effect,
of eelor codin
a. Extreme softenin of eoler ceding Or m&rkinglr
4. of cornpeaneat material,
5 I Complete destruction Of eemppOrt@rtt ma?tteria?I,
1 9
IN -R -QUA L- 67 -8
14. Effects of Cleaning Agents on Heat Shrinkable Tubing.
Heat Shrinkable Tubing - Scotchite 105C
Solvent
F reon TF
Freon TMC
1, 1, 1 , Tr ich lo- roe t han e
Alpha 563
Me thy le ne Chloride
3 0 S e c .
Imme rs ion Time
1 Min.
1
1
2
1
4
3 Mine
5 Mine
1
1
2
3
4
10 Min.
1
1
3
-
3
4
30 Min
1
1
3
-
3
4
- 1
H r . -
cI_
2 H r . -
- 4
H r . I__
NOTES: The heat shr inkable tubing w a s heated to shr inkage point. The tubing was brought to room t empera tu re and subnit*rgcyd in the cleaning agents .
Methylene Chloride softened the tubing from 30 Shore D to 10 Shore D.
K e y to Table E n t r i e s :
1. N o v i s ib l e effect.
2 .
3. E x t r e m e softening and blisterin
4. Complete dis integrat ion of matt3riaI.
Slight bubbling and softening and blistering.
20
LN- R - QUAL-67 -8
15. Comparison of Solvent's Effects on Hardness of F o r m i c a Board Before and Af ter 4 Hour Immers ion .
Solvents
Genesolv DTA
Methylene Chloride
1, 1, 1, Trichlo- roethane
Alpha 5 6 3
F r e o n TE
Freon TMC
Freon T F
Ethyl Alcohol
Shore Durometer Hardness - D Scale
In it i a 1 (Before Immers ion )
93
93
93
93
93
93
93
93
Fina l (After 4 Hr . Immers ion)
88
7 9
92
92
8 2
8 2
91
91
4
2 1
IN-R -QUA L-67 -8
16. dance with MSFC -SPEC -237A.
Acid Number Determination P e r f o r m e d in Accor-
Solvents
F r e o n T F
Genesolv DTA
Alpha 563
F r e o n TMC
Methylene Chloride
Acid No. KOH/GM Solvent
0.0034
0.0026
0 .0049
0.0100
0.0043
I t is not to be construed that the acid number of a solvent is the sole determinant of cor ros iveness and /o r de t r imenta l effects toward all types of m a t e r i a l s .
SECTION IV. CONCLUSIONS
A . S U M M A R Y
The r e su l t s der ived f rom cur ren t testing b y this laboratory and a review of the l i t e r a tu re and other laboratory data emphasizes the conclusions which a r e s ta ted o r implied b y mos t invest igators on the subject of postsoldering cleaning agents ,
The f ac to r s to be considered in the! choice of cleaning agent& age;
(1) The t ime of immers ion of pr inted c i r cu i t board mate- rials and components is crit ical , An immersion time of 30 seconds o r less is racornrnsnded for printed ci?= cui t assembl ies . This should include the total time (additive) i. e. after rework, r sso ldsr ing , ete .
( 2 ) The ma te r i a l s on which the soldering is per formed is to be considered. Detr imental effects of solvents differ with the composition of pr inted c i r cu i t boards
22
... .::fi:,. .::. .:i i
IN -R - Q U A L - 6 7 -8
B.
and the t ime of immers ion . ing Methylene Chloride are decidedly m o r e destruct ive to organic ma te r i a l s contained in pr inted c i r cu i t as- sembl ies as noted in the pure Methylene Chloride, F r e o n TMC, and Genesolv DTA. These solutions could not be approved without extensive tests and evaluation.
Cleaning agents contain-
( 3 ) The choice of cleaning agents m u s t be specific fo r the intended application. t e s t s on individual a s sembl i e s representa t ive of the work to be processed . General ly , i f the cleaning e€- fect iveness is sat isfactory, Ethyl alcohol, F reon T F (Trichlorotrifluoroethane) o r F reon TE-3 5 ( F r e o n T F with 35'7" ethyl alcohol) should be used. Alpha 5 6 3 o r a Trichloroethane may be used safely or, many pr inted c i rcu i t a s sembl i e s and a r e m o r e efficient in removing contaminates. pure chloronated hydrocarbon on the following mate r i m a l s :
It is n e c e s s a r y to p e r f o r m
Caution m u s t be exe rc i sed when using
Polyurethanes Silicones A c rylic s
OTHER CRITICAL FACTORS
(1) The detai ls of the method of washing and r insing fol- lowing solvent cleaning must be explicit, i, e . time of r inse , t empera tu re of solution , agitation, level 02
~ o n t a ~ i n a ~ i o n - f r ~ e solutions, s t c I
( 2 ) P o l a r ve r sus nonpolar solutions. Many p r o p r i e t a ~ y solutions contain both a polar and n ~ n p o l a r compaund that per form sa factorily, i , e * , tk@ nonpeiar eom= pound removes pound remov€!s active in The active a removed b y e i ther r ins s table polar and nonpolar solution, should be per formed to ascertain the cleanline@$ of
$irrou$ material$ and the pQlm eom-
Periodic t e s t s
23
IN-R-QUAL-67 -8
pr inted c i rcu i t assembl ies , e . g . , halogen ion t e s t o r conductivity elevation. contamination level of the final r inse solution.
This would a l so indicate the
( 3 ) The marking o r color coding on component p a r t s a r e ex t remely susceptible to damage by cleaning solutions These markings may be inks, paints, e tc . I with o r without a protective res in cover coating. After i m - mers ion of the p a r t into a cleaning solution, an a b r a - sive wiping action (for drying) removes many of the coatings. Whereas , a i r drying without rubbing allows the markings to " rese t" and retains its orginal adhe- sive proper t ies a
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